This invention relates to a magnetically operated display that provides a very wide visible viewing angle, excellent readability either in sunlight or darkness with relatively low power consumption.
Eye-catching displays are becoming more and more popular due to increasing consumerism and the desire for public awareness of products, public announcements etc. Particularly, the electronic changeable information displays have been accepted worldwide as an effective way for the communication between passengers and vehicle operators.
A first conventional display is the U.S. Pat. No. 5,005,305 by Turney et al. which discloses a magnetically operated display device including contrasting opposite sides and being mounted in a surrounding frame for pivoting about an axis. A permanent magnet within the display element has poles on opposite sides of the pivoting axis. A U-shaped electro-magnet has its pole pieces positioned on opposite sides of the pivoting axis where they may interact with the poles of the permanent magnet. The permanent magnet has a asymmetrical magnetic construction relative to the pivoting axis. When the electromagnet is energized, the repulsion at one pole of the permanent magnet is always greater than at the other pole of the permanent magnet, causing rotation of the display element. The display element is statically and dynamically balanced. The magnetically operated display device as disclosed by Turney et al. does not contain any emitting elements to illuminate the display especially in darkness time. Moreover, Turney does not specifically articulate both color similarity and contrast between its frame and flip element. The first conventional display shows clear images in a bright environment, however, visibility of the first surfaces of the pivotable plates is greatly reduced in darkness as the first surfaces of the plates do not produce light. Therefore, the magnetically operated display device as disclosed by Turney et al., due to lack of illumination elements, is not suitable for use inside a vehicle for the communication between passengers and vehicle operators.
A second conventional display is the U.S. Pat. No. 5,050,325 by Browne which discloses a display indicator with a movable element. The movable element is driven between ON and OFF positions by switching the polarity of a first high remanence magnetic core. A reed switch is located in the flux path of the switchable magnetic core and of a second magnetic core such that the reed switch assumes open and closed states. The reed switch is connected so that one state turns on or exposes a light source and the other state turns off or masks the light source. A plurality of light emitting diodes are located under the movable element for emitting light. However, since the tips of the light emitting diodes of Browne are not located beyond the brightly colored surface, the light emitted from the light emitting diodes does not illuminate the brightly colored surface of the movable element.
A third conventional display is the U.S. Pat. No. 4,264,906 by Wakatake which discloses a display element for use with a display panel which includes a display surface structure having a number of such elements arranged in a vertical plane and each adapted for rotation about support arms provided on the opposite side surfaces thereof, thereby producing a display of a character, graph, pattern, or the like on the display surface structure. The display element is formed with a plate-like (or four-cornered) block member having two (or four) display surfaces of different colors and one (or three) magnetic pieces. Although the display as disclosed by Wakatake provides two display surfaces of Different colors, it lacks an illumination source, therefore this display is not suitable for use in a vehicle for information communications between the vehicle operator and passengers.
A fourth conventional display is the U.S. Pat. No. 4,531,121 by Brown which discloses a visual display element, which may be used singly or as part of a large bank or like and similar elements, each element comprising an encasement, a slotted plate, and actuating assembly. The actuating assembly comprises a planar face with a colored pattern of lines thereon and is situated immediately behind and parallel to the slotted plate. When viewed from the front, the planar face and adjacent slotted plate, the slots of said plate comprise highly reflective surfaces, which collectively appear as a solid color. Selective relative movement between the planar face and the slotted plate causes the visually perceived color to change from one color to a contrasting color and thereafter back to the original color. Each visual display element does not have an independent light source. A light source, when and if needed, may be situated substantially to the rear of several display elements. However, the efficiency of the first conventional display is considerably reduced if the level of environmental light is increased, for example, a sunny day, and thus the noticeability of the display is impaired.
Displays used as the head sign or side sign mounted on vehicles normally have the following constraints:
1. Display needs to have a very wide angle: To provide passengers information, the display has to be readable to riding passengers. For a riding passenger, standing at the curb side to read a head sign mounted on the vehicle, the viewing angle for the display must be around 160.degree. minimum.
2. Contrast ratio: The display readability concerns its contrast ratio. The greater the ratio between the sign legend and sign background, the more readable becomes the display.
3. Pixel size: Due to space limitation on a vehicle, the pixel diameter is normally limited to between 10 millimeters (mm) and 25 millimeters (mm). For displays with a pixel diameter of less than 10 mm, it becomes cost-prohibitive for in the vehicle applications. A display made of small pixels to be readable at long distances (such as 400 to 500 feet), requires a lot of pixels to be stacked. Displays with pixel diameters greater than 25 mm, cannot provide enough resolution for efficient message display.
It is requisite to provide a display designed primarily for vehicle applications which can present clear images at both low ambient light and bright sunlight.